Using SLAR is an efficient, low-cost method of viewing and mapping terrains over a wide swath of territory on either side of the flight path of the carrier aircraft. Two SLAR antennas on either side of the aircraft illuminate a long, preferably narrow strip of the terrain with a high-powered short radar pulse, normally in the X-band of the microwave spectrum. As the radiated impulse power is reflected by the illuminated terrain and received by the now receiving SLAR antenna, the intensity and times of arrival of the reflections are processed electronically to produce an instantaneous terrain map. As the aircraft proceeds along its path the terrain map is updated. As an example a suitable radar pulse repetition frequency of 800 Hz could be used, with a pulse duration of approximately 250 nanoseconds. The quality of the terrain map depends strongly from the precision of the radiated illumination pattern. It is known in the art that a narrow beam in the horizontal plane (a so-called pencil beam in the azimuth plane) having its peak intensity along an axis perpendicular to the flight path and slightly inclined with respect to the horizontal plane, and illuminating the terrain with gradually declining intensity reaching a null underneath the flight path is required. Accordingly, the terrain is approximately uniformly illuminated irrespective of the distance from the antenna. A narrow beam in the horizontal plane is necessary in order to provide good azimuth resolution of the terrain of the strip just under the antenna as an illuminating radar pulse is emitted. Therefore, the far-field azimuth angle of the beam should be as small as possible, and the illumination intensity should decline from its peak at the near horizontal to the near vertical (downward from the aircraft) as uniformly as possible. These characteristics are, of course, desirable in any planar antenna array, and imply minimal side-lobe illumination.